Anomalously high radon concentrations in dwellings located on permeable glacialsediments

Abstract

Indoor radon concentrations were measured in different seasons in 104 dwellings located ona highly permeable ice-marginal moraine in Kinsarvik, Western Norway. The measurementsrevealed the highest indoor radon levels ever detected in Norway and extreme variations inseasonal and short-term indoor radon levels. Annual average indoor radon concentrations up to56 000 Bq m−3 and a meanvalue of 4340 Bq m−3 for the whole residential area are reported. By using the ICRP conversion factors toeffective dose, these indoor radon values correspond to a total annual effective dose of930 mSv and 72 mSv, respectively. By using the conversion as recommended by UNSCEAR,the effective doses would be about 50% higher. The indoor radon concentrations are foundto be strongly influenced by thermally induced flows of radon-bearing soil air directedtowards the upper part of the ice-marginal deposit in winter and towards the area of lowestelevation in summer. The pattern of seasonal variations observed suggests that inareas where thermal convection may occur, annual average indoor radon levelsshould be derived from measurements performed both in summer and in winter.